Superheat temperature control by overfire air



Nov. 30, 1954 w. H. ARMAcosT SUPERHEAT TEMPERATURE CONTROL BY OVERFIRE AIR Original Filed OC.. 14. 1949 I I l l Fan Speed Control lfw INVENTOR Wilbur H. Armocos'l' Y @57W ATTOR Y Fig; 2.

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Speed Control United States Patent() SUPERHEAT TEMPERATURE CONTROL BY OVERFIRE AIR Wilbur H.' Armacost, Scarsdale,N. Y., assignorfto vCom bustion Engineering, Inc., New York, lN. Y., a corporation of Delaware Suhstituted for applicationwSerial No. 121,239, October 14, 1949. This application July.14,-.:1-953,Serial/Nm temperature in vaporgenerating units. and` it has .special reference to an accomplishmentof .such .control through-a novel useof overre `airlin thefuel combustion chamber of the unit.

Broadly stated, the object of this invention .is` to control the superheated steam temperature by.utilizing secondary air streams to .direct either more .or less of. the. fuel combustion gases. either over or 4away from .thelsuperheater heating surface. l l i A more specific object is to adapt theforegoing novel form of control to A type` boilers wherein a superheater' is included in one `of two main boiler tube banks that incline downwardly and outwardly from a central upper drum and Whereinthe fuelis fired acombustion chamber beneath and betweensaid .boiler tube banks.

Another object is to apply ythesuperheat control means of this invention to the.` foregoing andfother boilers when fired by fuels such'as natural'gas or coal which require overre air .to enhancethe eiiiciency of 'thecombustion process.

Additional 'objects and advantages'will become apparent from the following description of `an illustrative tem# taken in `conjunction Vwith the accom-` bodirnent `when panying-drawing wherein:

Fig# 1 represents an-elevational cross- 'section of an A type steam generatingunit. taken on4 lin`ef1-1 of Fig. 2 and illustrating one preferred-mannerin which'the invention may be practicedand Fig. 2 is a plan section showing -a portion of `the ap#` paratus of Fig. .l as viewed online 2 2 -oftthatgurer Referring to the drawing; the A typesteam `generating unit there. represented comprises van `upperdrum 10 positioned centrally above two horizontally spaced i lower .drums 12 Vand .14 .and respectively interconnected therewith throughthe medium of leftand right tube .banks 13 `and 15. Steam generated in these :banks fpasses. from drum 10 through. conduitwl s to a superheaterl18 and leaves `the superheaterbywayof outlet 19.

In the illustrative-formushown, thissuperheater 1S is positionedin the left `bank-13 of boiler tubes; it is made up of hairpin-shaped `tube elementsltl disposed transversely ofzthefboiler tubes in Vsaid `bank .13; .and steam from conduit 16 enters inlettheaderzl,` thence passes through tube elements20 into intermediate header 22 and from this intermediate header passes through other. tube elements 20 'to outlet `header 23` and thence to outlet 19.

This steam generator of Figs. 1-2 may `be liredin any suitable manner such as by means of burners 25 mounted in an end wall 26 of the combustion chamber 27 formed beneath and between the left .and right'tubebanks 13 and 15 by the represented setting structure.' and the conventional casing structure `24 `which-surrounds the boiler banks.

Inthe illustrativel form shown each of these burners 25 consists of a centrally located fuelnozzle 29 through which natural gas or othersuitable fuelis admitted into the combustion chamber.:

Air for supportingcombustion also enters the combustion chamber 27 in surrounding relation to `the incoming fuel under the direction of `outer casing members 30. In`

the burner arrangement shown this airis made available to theburners by means `of awind box 31 `fed in any suitable manner as through a supply duct 32. This air may be under a small pressure created bya forced draft fan lice (notshown) orit mayibe broughtinto-the furnaceunder'. action of either natural draft or anrinduceddraft` the fan (.not shown) .connected withllue outlets. 34e-35.

The combustion ,gases resulting .from 'theburning offuel in chamber27 pass upwardly through boiler-tube banks 13.a'ndy 15 .and thence. out-.of the. boiler casing 24- by wayof .saidue outlets 34h-3,5.l .Theheat carriedv by these combustiongases .is given up to boiler heating.. surface 13-15 .as well as to thesuperheater surface 2i);l

but only the gases..passingthrough.boilerbank .13..are

instrumental in .imparting lto the superheater 13 heatfor'.

superheating. the steam-,generated inthe boiler.

it is well known. thatcertain fuels such `as ,natural gas requlre considerable excess airforelicient `combats-.-

tion, andI have therefore found it desirable.` to provide such excess .air through the medium of overtre jets. t. .In

the illustrative apparatus ,shown such jets are. represented at 37 and 38.

Air under pressure is .discharged through said jets. 37-33 `to provide penetration throughthegas mass in4 the combustion chamber and. to set up turbulence. which will bring the.`;air intomoreintimate contact with. the fuel and thereby speed up, theV `combustion process L audimake same more complete.

ln accordance withthe invention -air under thezrequired pressure "is supplied to the left set ofjets37 by f a fan 40 whose inlet is connected with .wind box 31rvia conduit 41 and. whoseoutlet leads to header .42.in communication with the .jets ,3'7g`and similarly air underthe required pressure is `supplied to the-right set of jets-38.

by a fan..44-whose. inletis connected with .wind .box 31` via conduit .45 and..whose .outlet leads to headery 46- in stant superheattemperature be provided .for-most efficientl operation of ,supplied .turbines landccertain. .other steami- :It is alsoknownthat varying-load. conditions on annA type steam .generator suchas here consuming` apparatus.

shown will` result.'inundesirable-variation in the .tem-

perature` of .the superheatedsteam .obtained `at outlet .19..

Thus, in the. absence -of .superheat control means low generator .will -be .accompanied steamv loadings U.on the by lowrsuperheat temperatures; mtermediate loadings on the generator .will -beacco'mpanied by intermediate .super-s heat temperatures; .andthlgh steam` loadings. on. the-genev erator will be accompanied by high superheat temperature.

In accordancetwith thisinvention it becomes. possible simply, readily -and .reliably to keep the .temperature of.

19.` constant through the entire range of loadings on the represented steam superheated steam. leaving outlet generator merely 4'by adjusting the relative .velocities of the overre `air issuing -fro'mtleft jets 37 and from right jets 38. In the. illustrative arrangement `shown such adjustment is accomplished` throughcontrol. of theoperating speeds of .left` and `right fans 40 and .44.

With thesetwo fans operating at substantially the same speed the total combustion gases liberated in the fur.

nace chamber 27 will divide substantially equallyin flowing through` left boiler tube bank 13 .and dischargeoutlets 34 and in flowingthrough right boiler tube bank 15 and dischargeoutlet 35. Under this condition substantially half of said total `gases will beinstrumental `in imparting heat to the superheater y1'8.

When however .by reason` of reduction in steam load or other cause the temperature` ofthe steam leaving superheater outlet `19 falls below` `the desired value, same maybe correctively raised either by increasing the speed of right fan44 or` decreasing the speed of` left fan `40.`

The effect in either'instance will be to flow a greater proportion of the total combustion `gases through lefty In. this y boiler tube bank 13 andl over superheater .18. way the superheated steam` temperature will be; correctively raised.

Likewise ifv byreason of increase in steam .load or for other cause the-.superheated steam..temperature .rises above thedesiredtv'alue, same may be .correctively lowered` either by increasing the speed of left fan 40-or by cutting down the speed of right fan-.44. .In either in- Paftented Nov. V30,1954

stance the effect will be to cause a greater proportion of the total combustion gases to flow through right boiler'V tube bank with consequent reduction in the rate at which heat is imparted to the superheater, 18. In this way the superheated steam temperature will be cor-' rectively lowered.

Obviously the required adjustment of speed control means 50-51 may be accomplished either manually or automatically. In the event of automatic control there can be used a conventional hookup which is actuated by the temperature of the steam leaving superheater outlet 19. Inasmuch as such automatic control facilities are well known no attempt to represent same is here made.

Moreover, adjustment in the velocity of the air streams issuing from jets 37 and 38 may be effected by running the fans 40 and 44 at constant speed and interposing a damper device in the outlet of each fan. In Fig. l such damper devices are indicated at 53 and 54.

From the foregoing it will be seen that this invention has provided novel means for effecting superheat control through the use of overfire air in vapor generators typified by the A type steam generating unit here shown and described. It will be understood however that the apparatus represented for practicing the invention is illustrative rather than restrictive and that other equivalent means for accomplishing the same or a similar purpose may be substituted without departing from the spirit and scope of the invention as claimed.

This application is a substitution of application Serial No. 121,239 filed October 14, 1949.

What I claim is:

l. In a boiler furnace, the combination of an upper drum, first and second banks of boiler tubes' extending generally downwardly and divergently outwardly from said drum, a superheater in said first boiler tube bank for raising the temperature of steam received from the drum, enclosure means surrounding combustion space beneath and between the aforesaid two banks of boiler tubes, a burner for introducing into said space fuel which in burning generates hot combustion gases that divide and pass upwardly and outwardly through said first and second tube banks, jet means along the second-bank side of said combustion space and spaced from said first boiler tube bank by substantially the full width of said combustion space, said jet means being positioned to direct a stream of air generally towards said first bank of boiler tubes opposite the jet means and through the combustion gases flowing toward said second bank of boiler tubes thereby agitating the combustion gases in a way tending to urge an additional portion of same through said gj,

first tube bank and over said superheater in that bank, and means for adjusting the velocity of said air stream whereby to control the proportion of the total combustion gases from said burning fuel which pass through said first bank over said superheater and which determine the temperature of the steam leaving the superheater.

2. In a boiler furnace, the combination of an upper drum, first and second banks of boiler tubes extending generally downwardly and divergently outwardly from said drum, a superheater in said first boiler tube bank for raising the temperature of steam received from the drum, enclosure means surrounding combustion space beneath and between the aforesaid two banks of boiler tubes, a burner for introducing into said space fuel which in burning generates hot combustion gases that divide and pass upwardly and outwardly through said first and second tube banks, jet means along the first-bank side of Sad combustion space and spaced from said second boiler tube bank by substantially the full width of said combustion space, said jet means being positioned to direct a stream of combustion supporting air generally over said combustion space and towards said second bank of boiler tubes opposite the jet means thereby agitating the combustion gases in a way tending to urge an additional portion of same through said second tube bank and away from said superheater in the first tube bank, and means for adjusting the velocity of said air stream whereby to control the proportion of the total combustion gases from said burning fuel which pass through said first bank over said superheater and which determine the temperature of the steam leaving the superheater.

3. In a boiler furnace, the combination of an upper drum, first and second banks of boiler tubes extending generally downwardly and divergently outwardly from said drum superheater in said first boiler tube bank for raising the temperature of steam received from the drum,

enclosure means surrounding combustion space beneath and between the aforesaid two banks of boiler tubes, a burner for introducing into said space fuel which in burning generates hot combustion gases that divide and pass upwardly and outwardly through said first and second tube banks, first jet means along the second-bank side of said combustion space for injecting into the aforesaid combustion gases a first stream of hot air directed towards said first bank of boiler tubes opposite the first jet means and tending to urge an additional portion of those gases through said first tube bank and over said superheater, second jet means along the first-bank side of said combustion space for injecting into said combustion gases a second stream of hot air directed towards said second bank of boiler tubes opposite the second jet means and tending to urge an additional portion of those gases through said second tube bank and away from said superheater, and means for adjusting the velocities of said first and second air streams whereby to control the proportion of the total combustion gases from said burning fuel which pass through said iirst bank over said superheater and which determine the temperature of the steam leaving the superheater.

4. In a boiler furnace comprising an upper drum, first and second banks of boiler tubes' extending genert, ally downwardly and divergently outwardly from said drum, a superheater in one of said two tube banks for raising the temperature of steam received from the drum, casing means surrounding said boiler tube banks and superheater and enclosing a combustion chamber beneath and between those banks', and burner means for introducing into said chamber fuel which in burning generates hot combustion gases that divide and pass upwardly and outwardly through said first and second banks, the combination of first and second jet means respectively disposed along the two tube-bank sides of said combustion chamber and respectively directed over said burner means towards the boiler tube bank on the opposing chamber side, air supply means causing each of said first and second jet means to blow into the aforesaid combustion gases a stream of hot air which agitates those gases and tends to urge same through the boiler tube bank on the opposing chamber side, and means for varying the velocity of the air streams issuing from one of said first and second jet means where- V'by to adjust the proportion of the total combustion gases from said burning fuel which pass through the tube bank wherein said superheater is included and which thereby determine the temperature of the steam leaving said superheater.

5. In a boiler furnace comprising an upper drum, first and second banks of boiler tubes extending generally downwardly and divergently outwardly from said upper drum to first and second lower drums horizontally spaced one from the other, a superheater in one of said two tube banks connected with said upper drum and disposed to raise the temperature of generated steam discharged therefrom, casing means surrounding said boiler tube banks and superheater and having an upper portion that is open for gas discharge and a lower portion that encloses a combustion chamber beneath and between said first and second banks, and burner means for introducing into said combustion chamber fuel which in burning generates hot combustion gases that divide and pass upwardly through said first and second banks, the cornbination of first and second sets of jets respectively disposed beneath said lower drums along the two tube-bank sides of said combustion chamber and respectively directed over said burner means toward the boiler tube bank on the opposing chamber side, hot gaseous fluid combustion supporting supply means causing each of said first and second sets of jets to blow into the aforesaid combustion gases streams of gaseous fluid which agitate those gases and tend to'urge same through the boiler tube bank on the opposing chamber side, and means for varying the relative velocities of the gaseous fluid issuing from said first and second sets' of jets whereby to adjust the proportion of the total combustion gases 'thereby determine the temperature of the generated steam leaving said superheater.

6. In a boiler furnace having a lower portion and an upper portion formed with adjoining passes, the combination of two tube banks arranged in the adjoining passes in the furnaces upper portion and adapted for parallel upwardly directed ow of combustion gases therethrough, a superheater in one of said two tube banks for raising the temperature of steam from those banks, a burner in the furnace chambers lower portion for there introducing fuel which in burning generates combustion gases that divide and pass upwardly from the chamber through said two tube banks, and means positioned along each of said tube-bank sides of the combustion charnbers lower portion for directing streams of gas into the furnace, said means being so located and directed that the streams of gas projected from each side pass generally over the location of the burning fuel toward the bank of tubes at the opposite side, and means elective to vary the relative entering velocity of the projected gas at said two sides within limits determining the proportion of the total combustion gases from said burning fuel which passed through the tube bank wherein said superheater is included.

6 7. A boiler organization as deined in claim 6 wherein the gas projected from each side of the combustion chambers lower portion is air.

8. A boiler organization as defined in claim 6 wherein the boiler is of the marine A type.

References Cited in the lile of this patent UNITED STATES PATENTS Number Name Date 1,038,812 Yarrow Sept. 17, 1912 1,114,785 Meier Oct. 27, 1914 1,184,977 Meier May 30, 1916 1,931,948 Armacost Oct. 24, 1933 2,245,209 Mayo June lO, 1941 FOREIGN PATENTS Number Country Date 2,963 Great Britain Feb. 5, 1902 373,860 Great Britain June 2, 1932 

